On Feb. 5, 2021, the United Kingdom (U.K.) Supreme Court issued its judgment in R (on the application of KBR, Inc) v. Director of the Serious Fraud Office, holding that the U.K. Serious Fraud Office (SFO) lacked statutory authority to compel a U.S. company to disclose overseas data under threat of criminal sanction. This judgment has obvious similarities with the so-called Microsoft Ireland decision of the U.S. Second Circuit Court of Appeals, which held that using U.S. Stored Communication Act (SCA) warrants to reach overseas data was an impermissible extraterritorial application of that legislation. Microsoft Ireland was viewed by many as hugely controversial, hindering U.S. law enforcement’s access to overseas data, leading to a Supreme Court appeal and, ultimately, legislative amendments. This new U.K. judgment promises to have an equally significant impact across the Atlantic on equivalent U.K. law enforcement powers.